How many 'steps' in one degree of movement?

[pspitael]

Is there any correlation between one 'step' move with my SG2100 motor in terms of the fractions of degrees that makes the motor move?

Or if I select the '1 second' move - same question, is there any correlation?

Thanks!

 

[SatelliteAV]

No correlation. In addition, the amount of distance between orbital degrees is tighter near the horizon than it is near the top of the arc.

 

[Larobpra]

If I recall from when I had a SG2100, 8 clicks would move the dish 2 degrees.

 

[Anole]

If you are talking about actual satellite orbital positions when you say degrees, then Brian is correct.

However, you may find a seemingly fixed number of steps between satellites which are predomently overhead.
But once you compare to satellites far from overhead (closer to the horizon), you'll see fewer steps.

If you were at the center of the earth, all would be equal.
But since we're on the surface, it's not.


edit: and on BUDs, driven by those telescoping actuators, the movement is even worse!
Five steps on the east side of TS is different from five on the west side
Even very near the center of your arc
But chalk that up to the geometry of the mount!
Only true H-H BUD mounts/positioners work like your 2100
.
2nd edit: especially on H-H BUD mounts, you may find talk of "how many steps" to go between satellites, or across the users arc.
One member may have 800 steps from 50w to 137w.
Another may have 1600. Obviously, the second can position more accurately.
In a thread, Pendragon described a shaft encoder which gave him maybe 4000 or 8000! *
At that point, you worry about the slop on your gear train!

And MY point is that it's sometimes useful to talk about average steps per degree or across the arc, even though they're not consistent.


* I don't recall exact numbers, but my examples are in the ballpark
.

 

[gpflepsen]

If you are talking about actual satellite orbital positions when you say degrees, then Brian is correct.

However, you may find a seemingly fixed number of steps between satellites which are predomently overhead.
But once you compare to satellites far from overhead (closer to the horizon), you'll see fewer steps.

If you were at the center of the earth, all would be equal.
But since we're on the surface, it's not.

Actually, it's how far you are from the axis of the earth, not the center. If you're on the north or south pole (on a tall enough tower to see the sats, ~60 miles) the orbital positions (degrees) are equally spaced.

 

[toucan-man]

Who'd want to live there ?

 

[tekjunkie02]

Actually, I found the "1 second" feature very handy for finding the sats at first.
The motors manual states the amount that the motor rotates in degrees per second and gives you both the 13v and 18v speed. These can be used with the azimuth angles from your location to get you very close to your target. Using your azimuth angles makes it relevant to your location.

 

[Tron]

I have a friend who put an old BUD up, and uses a security camera and monitor to judge actuator movement. He has marked the monitor where the dish should be at any given orbital position, and his method actually works well ...

 

[pspitael]

Thanks for the tip tekjunkie02. I did go back and find a manual, and you're right, it gives the speeds for 13V and 18V. i guess I don't know which voltage my receiver is using, it's set to 'auto'. If I peg it to one voltage (which I could) - is there an advantage to using 13V or 18V?

 

[updatelee]

18v is faster and more powerful.

I dont know how other apps/receivers do it, but I would think its common practice if the lnb is set to H/V then it should switch to 18v, move the motor, then switch to the selected voltage once done. Maybe some just use the selected voltage so that it will acquire a lock faster and not have to wait to timeout. It would be nice if the motor would signal when done, but they dont. I just use a preset time, I think I do 1.5sec per degree of movement.

UDL

 

[pwrsurge]

18v is faster and more powerful.

I dont know how other apps/receivers do it, but I would think its common practice if the lnb is set to H/V then it should switch to 18v, move the motor, then switch to the selected voltage once done. Maybe some just use the selected voltage so that it will acquire a lock faster and not have to wait to timeout. It would be nice if the motor would signal when done, but they dont. I just use a preset time, I think I do 1.5sec per degree of movement.

UDL

Don't know about other receivers but the AzBox miniMe American Edition does have an option to "use 18V while the motor is moving". When enabled, it essentially sends out 18V until the motor is done moving even when tuned to a vertical channel based on a user configured motor rotation speed.


Best regards,

PwrSurge
AzBox Canada

 

[SatelliteAV]

Don't know about other receivers but the AzBox miniMe American Edition does have an option to "use 18V while the motor is moving". When enabled, it essentially sends out 18V until the motor is done moving even when tuned to a vertical channel based on a user configured motor rotation speed.

Is that function automatically disabled when bumping the dish to optimize DiSEqC1.2 positioning or does it need to be manually disabled when fine tuning? We had played around with this feature with the microHD, but didn't like how it prevented vertical transponder reception until the motor position was set.

 

[xtgold]

some old receivers like the old coolsats had a coarse and fine movement selection for moving the motor.I miss that on the modern receivers.

 

[gpflepsen]

I've got a spreadsheed that will return the degrees between satellites that a polar mount must move, if anyone wants to play with it. You can put in your lat and Lon, then the two satellite positions.

Like was said earlier, the degrees of motor rotation/degrees of satellite orbit are maximum at the equator and center of the arc. Motors must move ~1.3 degrees per degree of orbital there. It drops to almost 1:1 at the horizon. In the center of the lower 48 states, it is about 1.12 degrees between orbital degrees at the center of the arc.

 

[tekjunkie02]

Sorry I didn't see this sooner.. It's the same voltage the receiver is sending to the LNB(F), so it changes when you change polarity. What I did, was, determine the active transponder on the satellite I wanted to find, enter that into my Traxis 6000, then calculate the azimuth angle difference between where the dish is now, vs. where it has to go, then divide that by the motor speed/sec at the voltage for that polarity. That will tell me how many seconds the motor needs to run to get there. Then use the "1 second" movement til I get to where only fractional time is left, then switch to "step" movement and keep watching Sig and Qual til they're peaked.
The Traxis 6000 receiver makes this very easy because it has the 1-second movement option, so you don't have to try and time it yourself

I used the "Dishpointer" site to get "my" angles for each satellite, and I used "alt-prt scrn" to save a copy of each sat's specs as a picture in a folder that I called "sat-looks", that way I have them for whenever I need them. Took a while to copy and paste them all, but, having them has come in very handy for me.

Hope this helps!

 

[pspitael]

Thanks for all the feedback folks.

gpflepsen - I wouldn't mind looking at your spreadsheet if you're willing to share...

tekjunkie02 - I'm pretty much still figuring all this out, so I don't understand the link between voltage and polarity. Regardless, I'm assuming you go through this routine essentially when setting up your receiver/satellites initially, not every time you tune to a satellite? Sounds like you've thought about this more than I have! But your explanation makes sense. I'll have to toy with my Traxis 6000/SG2100 setup a bit more and see if I can get pretty close to predicting how many 1 second movements it would take...

 

[tekjunkie02]

Thanks for all the feedback folks.

gpflepsen - I wouldn't mind looking at your spreadsheet if you're willing to share...

tekjunkie02 - I'm pretty much still figuring all this out, so I don't understand the link between voltage and polarity. Regardless, I'm assuming you go through this routine essentially when setting up your receiver/satellites initially, not every time you tune to a satellite? Sounds like you've thought about this more than I have! But your explanation makes sense. I'll have to toy with my Traxis 6000/SG2100 setup a bit more and see if I can get pretty close to predicting how many 1 second movements it would take...

Yes, this is only needed when you are trying to find sats with nothing but the motor speed and the azimuth angles.
the Traxis 6000 is excellent for this... it's really quite simple, let me try an example.
The voltage, is the voltage that is sent to the motor, it is the same voltage that is sent to the LNBF, so for Horizontal Transponders it is 18v, and 13v for Vertical.
The motor I have moves at 2.4 degrees/sec at 18v and 1.5/sec at 13v.
If I am currently at my southernmost sat AMC9 at 83w and I want to hit the 72w sat;
I would select TP 12053V ...that would set the output voltage at 13v for Vertical,
then, I would subtract 159 from 180.2.... 159 is my azimuth angle for the 72w sat, 180.2 is for the 83w sat, so the result is I need to move 21.2 degrees with my motor.
so, then divide 21.2 by the 1.5 rotational speed at 13v, and I find I must move east for 14.1333.. seconds.

I hope that helps explain it... it's really much simpler than the explanation makes it sound...LOL

 

[gpflepsen]

gpflepsen - I wouldn't mind looking at your spreadsheet if you're willing to share...

No problem. The diagram is from the viewpoint above the North Pole, with your position to the right along your longitudinal line that corresponds to the latitude. The top of the arc (due south) is also to the right. The angles to the satellite positions are referenced from due south (to the right), positive cc and negative cw. If you put in angles that are not realistic, as in more than 90 degrees from your position, the results will not be what you expect.

 

[pspitael]

Thanks all!

 

[tekjunkie02]

gpflepsen,

Are the angles that we use relative to the earth's axis as the longitudinal lines are, or, are they relative to the motors position on the earth's surface?

It's been so long since I used this procedure that I don't really remember now if my statement above was correct. Is it the difference between azimuth angles that we are moving, or the difference between longitudinal positions?

I thought it would be the difference in azimuth's that we needed for the amount the motor had to rotate, but somehow, my calculation in my example above (14 seconds to move from 83w to 72w) doesn't sound right?

I'm confused...LOL, again